Back in 1993 to 1994, I was involved a project in Interstate Highway I10
near Beaumont, TX. We used FWD, and Rolling Dynamic Deflectometer(RDD)
(Developed from UT Austin) to determine the extent of pumping . RDD is
similar in nature as FWD but it moves continously about 1 to 2 miles per
hour. RDD conducts the dynamic tests every few inches. Using data
processing, it can measure stiffness with depth every 5 to 10 ft intervals.
It can detect the change of stiffness with depth. RDD finding is very
successful especially in determining the load transfer between the slab.
Since the pumping is most likely occurred along the joints. The change of
load transfer (good versus bad) is a very useful information related to the
extent of pumping(ie. Erosion).
Other techniques in determining the extent of pumping is using micro-camera
with drill bit as the drill rod advances, the video picture can be seen at
the surface and it can estimate the extent of void under the concrete
pavement.
James Lee, PhD.
Caltrans, USA
916-657-3962
David Cebon <[log in to unmask]>
Sent by: "The list is for the To:
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technical, op" Subject: Fwd: Determination/Monitoring of
<ROAD-TRANSPORT-TECHNOLOGY@JISCM erosion below concrete
AIL.AC.UK> slabs/pavement s
04/26/02 07:43 AM
Please respond to "The list is
for the use of academics and
others interested in
technical, op"
Dear research colleagues,
After my question on how to judge a concrete pavement after 10-13 years in
a
Design-Construct/Build-Maintain contract I gt quite a lot of suggestions.
However, in a brainstorm session we derived at the conclusion that we don't
have a real working system or equipment to judge the (remaining) structural
design life of the pavement after 10-13 years. Of course you can count the
number of cracks etc and even measure the deflections although these will
be
very low but still you don't have or get knowledge about the situation at
the bottom of the concrete pavement. To complicate the problem it is
required that the concrete surface will be covered with a porous asphalt
layer (noise reduction). One major problem is possible existence of erosion
problems. When you see that the porous asphalt is very dirty by fine
aggegrates or that trucks are pumping this out of the pavement you are
already too late.
Therefore I would like to ask your attention for the following question(s):
1. Do you know references in which the erosion process below concrete
pavements is monitored and which (ndt) equipment is used.
2. Do you have suggestions how to measure in a non destructive way a
quantity which can be related to the amount of erosion.
(Wave-speed/SASW || Ground Radar Penetration || Capacity
measure :: Relation with the density)
It will not be possible to carry out destructive monitoring tests but it
will be possible to build in something like a steel plate in the base below
the concrete pavement .
Looking forwards to your reaction and thanks in advance
Ad Pronk
Road & Hydraulic Eng. Div.
Rijkswaterstaat
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